The present invention relates to a hydrostatic gear ring machine.
Gear ring pumps or motors, above mentioned as hydrostatic gear ring machines are known in the art. The hydrostatic gear ring machine of the type under discussion include a gear ring piston which generates reaction forces by means of a parallel crank gear or drive. If the shaft of such a machine is rotated by a motor the machine is operating as a pump; if, however the shaft of the machine is not driven by a motor but high-pressure liquid is fed to the inlet opening of the machine, and the liquid will rotate the gear ring and the pinion the machine will operate as a motor.
The above mentioned parallel crank gear imparts to the piston a circular movement with some amount of eccentricity, without however, permitting the ring-shaped piston to rotate independently relative to the housing of the machine. The parallel crank gear of conventional machines includes circular tooth gaps formed on the disc-shaped piston, and circular teeth which are formed as cylindrical pins on the housing. Such parallel crank gears are for example applied with the well known "Cyclo Gear". In conventional gear ring machines circular teeth gaps, in which the cylindrical pins are engaged, are each formed by one third of a circle. Therefore dimensions of the machine as well as expenses for the manufacture of its components are smaller.
As has been mentioned above the parallel crank gear of the known gear ring machine transmits all the reaction forces of the slow-running motor to the housing with high torques. Since the operational mesh angle of such parallel crank gear is very unfavorable the transmission of the high torques has a very bad effect on the housing and a fine rolling friction is not obtained in the parallel crank gear. Particularly during the start of the machine at high loads high friction losses occur in such gearing, which under circumstances can, together with friction losses occurring in the displacement gearing, forming chambers of different volumes, cause a self-jam or self locking in the interior of the machine. For this reasons slow-running gear ring piston machines are not suitable, for example in cable winches because there full loads must be easily manipulated on suspenders.
In such known machines the inner toothing, forming the displacement chambers, has in many positions a very unfavorable pressing angle so that high friction occurs in many angular positions if the machine is operating under high pressure loads and also under high torque loads.
Hydrostatic gear ring machines have been disclosed, for example in applicant's U.S. Pat. Nos. 4,398,874 and 4,432,732.